Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KPHI 270143 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 943 PM EDT TUE JUL 26 2016 .SYNOPSIS...
-- Changed Discussion --
A weak cold front will continue to slowly drift south across the region overnight before stalling nearby to our south Wednesday into Thursday. Several waves of low pressure developing along this boundary will result in periods of showers and thunderstorms late in the week and this weekend.
-- End Changed Discussion --
&& .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
-- Changed Discussion --
The weak cold front is more tough to find now that the winds are light to locally calm. Now that the mixing has waned, the dew points have increased some for much of the area. The exception is portions of the Poconos. The leftover boundary looks to remain in our vicinity overnight. All the convection remains to our southwest so far where instability is greatest and some short wave energy is moving eastward. Prior to losing the visible satellite imagery for the day, there appeared to be a convectively induced short wave cresting the Appalachians of West Virginia to western Maryland. This feature moved out of southern Ohio earlier. The forecast challenge is does this feature develop some convection across our southern areas well after Midnight. The HRRR and RAP show some development after about 06z in the Philadelphia metro. The model guidance generally show dew points and elevated instability increasing overnight across mainly the southern zones. This is low confidence and therefore we maintained mostly slight chance pops from about northern Delaware southward overnight. Otherwise, some increase in high to eventually some mid level clouds across at least the southern half of the area. Across the northern areas especially for awhile, radiational cooling and some lower dew points and very light winds has allowed the temperatures to drop a bit faster. Patchy fog may develop before sunrise across northeastern PA and northwestern NJ.
-- End Changed Discussion --
&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... Some of the model guidance shows the cold front moving south of Delaware Wednesday morning while others keep the front stalled over our southern zones. Given it`s the middle of the summer and zonal steering flow aloft, we favor a more northern solution with the front stalling in the Delmarva. Expect additional showers and storms to develop along the lingering boundary during peak heating hours tomorrow afternoon. Clouds near the front will likely keep temperatures down a few degrees in DE and eastern MD (upper 80s) while stronger heating under mostly sunny skies in eastern PA and NJ will allow for temperatures to climb back into the 90s. However, we are looking at low 90s for highs and humidity levels will be comfortable with dewpoints in the 60s. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... The front will remain fairly stationary over the Delmarva Wednesday night into Thursday before starting to push back north as a warm front Thursday night into Friday. This boundary will act as a focus for weak low pressure development. These waves will then ride along the boundary and will result in a flare-up of showers and thunderstorms. Specific timing for this can be tricky and subject to change, but current thinking is for Thursday night into early Friday and then again on Saturday. Outside of these times, expect generally diurnal driven climatological threat of showers and thunderstorms. After a bit of a reprieve with lower humidity levels mid-week, dew points will increase back to 70-75 over the Philadelphia metro area, southern New jersey and the Delmarva by Thursday and Thursday night. This will push the heat index values into the upper 90s, almost 100 on Thursday. After that, expect lower heat indices for Friday and the weekend as high temperatures will be suppressed by increased cloud cover. It appears that the weather will remain warm, muggy and unsettled through the start of the next week, before the frontal boundary finally sinks far enough south to allow a marginally cooler, but drier airmass the infiltrate the entire region. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Mainly VFR through Wednesday. Patchy fog may develop late tonight in the fog-prone terminals (e.g., RDG, MIV). There could be a shower or thunderstorm well after Midnight near ILG and perhaps to PHL, however this is of low confidence. Showers and storms Wednesday afternoon are expected to stay south of the terminals (but it will could be very close by to ILG- MIV- ACY). Light and variable winds tonight, however locally southwest for awhile especially at PHL and ILG. The winds generally west- northwest 5-10 knots on Wednesday but the sea breeze will likely result in a wind shift out of the south- southeast at ACY and MIV. The sea breeze front could make it to the I-95 terminals toward sunset. Outlook... Wednesday night through Sunday...Mainly VFR conditions expected. Scattered showers and thunderstorms Thursday, Friday and Saturday, with MVFR/IFR conditions possible with any shower and thunderstorm activity.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
The winds are expected to turn around toward the north late tonight especially across the northern and central zones as a weak front moves southward. The winds should then turn southerly Wednesday afternoon as a sea breeze develops. Speeds should remain under 20 knots. Wave heights on our ocean waters are expected be 2-3 feet through the period. Waves on Delaware Bay should be 2 feet or less. Outlook... Wednesday night through Sunday...Sub-advisory conditions are expected to continue on the area waters through the forecast period. Expect higher winds and waves in and near scattered showers and thunderstorms that will be more likely at the end of the week.
-- End Changed Discussion --
&& .CLIMATE... The last time the temperature reached or exceeded 98F at PHL was three years ago on July 18, 2013. The last 100-degree day at PHL occurred four years ago on July 18, 2012. Record high temperatures for Wednesday and Thursday are below. Site 27th 28th ---- ---- ---- PHL... 101-1940 100-1941 ABE... 98-1955 97-1949 ACY... 99-2005 98-1999 ILG... 100-1894 101-1894 TTN... 100-1894 101-1894 GED... 98-2005 99-1949 RDG... 98-1955 99-1941 MPO... 91-1955 93-1949 && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...JK Near Term...Gorse/Klein Short Term...Klein Long Term...JK Aviation...Gorse/Klein/JK Marine...Klein/JK Climate...

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.